It should be added, that after the machine begins to work, and the water has risen into and filled the force-pipe, it fills also a little cistern, and by that means fills another pipe, called the condensing-pipe, which may be turned either way, over any of the receivers, when either is thoroughly heated by, the steam, to condense it within, thereby producing a vacuum, which absorbs the water out of the well into the receiver, on the principle of a syphon. Also a little above the cistern goes another pipe to convey the water from the force-pipe into the lesser boiler, for the purpose of replenishing the great boiler, when the water in it begins to be almost consumed. Whenever there is occasion for this, the cock is to be turned which communicates between the force-pipe and the lesser boiler, to close it effectually; at the same time having put a little fire beneath the small boiler, which will grow hot; its own steam, which has no vent to escape, pressing on its surface, will force the water up another pipe, through an aperture in the great boiler, and so long will it run, till the surface of the water gets so low as to be beneath the bottom of the pipe of communication--then the steam and water running together, will cause the valve (called a clack) to strike, which will intimate to the operator that it has discharged itself into the greater boiler, and carried in as much water as is then necessary; after which, by turning a cock, as much fresh water is let in as may be necessary; and then, by turning another cock, new fresh water is let out of a recipient into the less boiler as before; and thus the engine is supplied without fear of decay, or any delay in the operations; and proper attention in the workmen is only necessary to prevent disorder in a machine so expensive and complicated. Also, to know when the great boiler wants replenishing, turn the gauge-cock; if water comes out, it does not need a supply; but if steam alone, then the want of water is certain. The like with the cock with which the lesser boiler is prepared for the same purpose, when the same state will be marked by like results. In working this engine, very little skill, and less labour is required: _Attention_ is the chief requisite; it is only to be injured by want of due care, extreme stupidity, or wilful neglect. The engine described above, does not differ essentially from that first designed by the inventor, Captain Savery; the chief alteration which now occurs, is only in some few slight particulars. For example, the original engine had only one boiler, and there was no ready means for supplying it with water, to remedy the waste occasioned by evaporation of steam, without stopping the action of the engine, whenever the boiler was emptied to such a degree as to risk burning the vessel. After it was replenished the machine had to remain idle till the steam was raised, thus causing an immense loss of time; which is remedied by the application of a second boiler.